This invention relates in general to sensors for toxic gases and, more particularly, to a detector system for toxic gases permitting convenient, reliable, replacement of a battery and gas sensor in a housing containing the system.
Airborne toxic gases and vapors, such as carbon monoxide, mercury, ethylene oxide, volatile organic compounds, hydrogen sulfide, etc. are difficult to detect, especially where they are odorless or present at levels that cannot be smelled or are masked by other odors. The danger of these is becoming increasingly apparent, especially in industrial plants, mines, well-sealed homes and office buildings, recreational and other vehicles and other environments in which people are present for long periods.
Recently, a solid-state biomimetric sensor has been developed by the inventor of the present application which has an extended useful life and which mimics the human response to various toxic gases and vapors. As described in U.S. Pat. No. 5,063,164 this sensor comprises a porous, semi-transparent substrate with a self-regenerating chemical sensing reagent impregnated into the substrate. The optical density of the chemical sensor changes in response to contact with the toxin. This patent describes a variety of sensing reagents and substrates. Some perform at optimum levels under high humidity conditions, while others require low humidity for optimum performance.
The sensor has a relatively long useful lifetime, typically about three years, approximately equivalent to the useful life of typical alkaline battery.
Other gas sensing compositions have been developed, such as those described by Shuler et al in U.S. Pat. 4,043,934. The disclosed sensing reagents effective with certain gases, such as reducing gases like carbon monoxide, producing a color change upon exposure. These materials, however, tend to have a short useful life, typically 2-4 months.
In order to apply these toxic gas sensor materials in practical applications, such as home or recreational vehicle use, compact, reliable, easily serviced sensing and alarm systems are needed. The system must provide accurate and reliable detection of optical transmission characteristics and/or color changes. Characteristics of certain sensor materials, such as variable response depending on ambient humidity, must be accommodated. Ease of servicing, e.g., replacement of the sensing material and battery, battery pack or main power supply, assurance that a battery or power supply is in place, is an important consideration where unskilled persons are maintaining the system.
It is, therefore, an object of this invention to provide a simple and reliable system for detecting toxic gases. Another object is to a provide system which is easily serviced to replace the sensor and battery at appropriate intervals and prevents the use of the system without a battery in place. A further object is to provide a system which can accommodate sensing materials of different types, e.g., color change, optical density change and different humidity sensitivity.